The present invention relates to injection molding and in particular to an injection nozzle system.
Temperature control of the melt as it exits the tip of an injection nozzle is often critical to successful injection molding. If the temperature rises too high degradation of the melt will result and if the temperature falls too low the melt will clog up the system.
One approach to controlling the temperature of the melt at the tip of the nozzle is to divert the melt so that it exits the nozzle tip from a side opening (see for example U.S. Pat. No. 5,658,604 (Gellert)). The melt then collects in a gathering space surrounding the tip before it passes through the mold gate. The advantage of this approach is that the resulting greater mass of the tip below the side opening improves heat transfer from the tip to the melt collecting in the gathering space. A problem with this approach is that the diversion of the melt effects the even flow of the melt through the system. Also, the diversion through a side opening introduces the melt to relatively cooler surfaces of the melt plate that tend to cool the melt excessively.
It is also important that the nozzle tip be located accurately within the nozzle body to ensure that the respective melt channels align.
Slight variances in the diameters of the nozzle tips and the bores of the nozzle bodies, or in the thread engagement between the nozzle body and nozzle tip, can lead to slight misalignments of the respective melt channels. Such misalignments can negatively effect the flow of melt through the nozzle.
The present invention provides an improved nozzle system that overcomes the problems discussed above.
In one aspect, the invention provides a nozzle tip for an injection molding machine, said nozzle tip comprising:
a body having a first portion and a second portion;
a melt channel extending from an inlet defined in said first portion to an opening defined in said second portion, a first section of said melt channel extending from said inlet along a first axis, a second section of said melt channel extending from said first section along a second axis that is inclined relative to said first axis and a third section of said melt channel extending from said second section along a third axis that is parallel to and eccentric from said first axis, wherein a straight through channel is defined in said melt channel parallel to said first axis from said inlet to said opening.
In another aspect, the invention provides a nozzle system for an injection molding machine, said nozzle system comprising:
a nozzle body defining a first melt channel and a bore along a common axis, said nozzle body having a first connector;
a nozzle tip defining a first portion sized to fit in said bore and a second portion for protruding from said bore, said nozzle tip defining a second melt channel;
a first tapered engagement surface defined on said second portion of said nozzle tip; and
an alignment member having a cylindrical sleeve with a second connector for releasably connecting said alignment member to said first connector of said nozzle body, said alignment member defining an aperture coaxial with said cylindrical sleeve, said aperture having a second tapered engaging surface for engaging said first tapered engaging surface on said nozzle tip to locate said nozzle tip in said nozzle body with said first and second melt channels aligned along said common axis.